Glass sheets are bent and quenched to provide a desired shape for a particular application and to improve the mechanical characteristics of the bent glass sheet, respectively. Typically, the glass sheet to be bent is heated to its deformation point of about 1200.degree.-1300 F. and then bent to the required shape before being rapidly cooled by an air spray to temper the glass. Tempering greatly increases the mechanical strength of the glass and its resistance to breakage as well as causing the glass to break into small relatively dull pieces when broken instead of into large sharp slivers as in the case with untempered glass. Glass sheets have been known to be sag bent on horizontal molds having a curved bending surface on which a glass sheet is placed on the bending surface and heated to a bending temperature where the sheet sag bends under its own weight to conform to the shape of the bending surface. Heat softened glass sheets have also been known to be press bent between male and female members of a press bending mold. In addition, glass sheets have been known to be bent on vacuum molds.
Conventional glass sheet bending operations typically involve a two-step bending and quenching operation where bending and tempering take place at different stations. In some conventional press bending operations, press face distortion occurs to the bent glass sheet. Once the heat softened glass sheet is bent at the bending station it must be transported to a quenching station where the bent glass sheet is exposed to an air spray to temper the glass sheet. As the glass is being transported, roll marking has been known to occur as well as premature cooling prior to the quenching step resulting in a partial tempering of the bent glass sheet. Also, once the glass sheet arrives at the quenching station, the quenching air typically is applied in a non-uniform manner with respect to the bend in the bent glass sheet causing unbalanced rates of cooling over the surface of the glass sheet. Furthermore, the exit temperature of the glass sheet in a two-step operation must be higher to allow for the increased transportation time of the heated glass sheet.
Prior art reference noted by a search conducted prior to filing this application are discussed below. U.S. Pat. No. 4,277,276 to John D. Keller et al provides a vacuum mold capable of defining a flat configuration or a selected curve configuration that is capable of engaging a heat softened flat glass sheet by applying vacuum while engaged with the glass sheet in the flat configuration and bending the glass by deforming the mold to the selected curve configuration. The curved glass sheet is quenched at a quench station separate from the bending station where the vacuum mold is located.
U.S. Pat. No. 4,236,909 to Dean L. Thomas et al provides an apparatus for heat strengthening glass sheets which includes a cooling station and a set of nozzles on each side of a path of glass travel to thereby force cool the glass sheets at a more rapid rate than its normal rate of cooling. No bending is provided for by this apparatus.
U.S. Pat. No. 4,203,751 to Mario Roth et al provides a process utilizing vertical male and female mold members having center and jointed elements. The molds are brought together to confine a heat softened sheet of glass between the center elements and the jointed elements are simultaneously moved to bend the portion of the sheet engaged between the jointed elements with respect to the center portion of the sheets. No quenching apparatus is provided.
U.S. Pat. No. 2,223,124 to William Owen provides a method and apparatus for bending and case hardening glass sheets on a horizontal runway having rolls which are movable to sag so that the peripheries of the rolls engaging the lower surface of the glass sheet describe the curvature to which it is desired to bend the sheet. The bent glass sheet is quenched by air blasts eminating from stationery nozzles that do not conform to the shape of the bent glass sheet resulting in non-uniform cooling of the glass sheet. Also, no topside bending surface is used requiring higher glass sheet temperatures to bend the glass sheet.